One typical testing system that utilizes inflatable packer elements is disclosed, for example, in U.S. Pat. No. 3,439,740, issued to G. E. Conover. Both of the inflatable elements are expanded by a downhole pump that is actuated by rotation of the pipe string that extends from the tools to the surface. Such rotation causes a transversely oriented cam system to reciprocate a plurality of pistons or plungers which alternately draw in well bore fluids and supply them under pressure to the inflatable packing elements through fluid passages controlled by check valves. When a predetermined inflation pressure has been developed within the elements, a relief valve opens so that fluids are vented to the well annulus to prevent the development of excessive pressures. When it is desired to deflate the packing elements, further rotation is utilized to actuate an unloader valve and thereby bleed off the inflation pressure.
Another drill stem testing system of the type described is disclosed in U.S. Pat. Nos. 3,876,003 and 3,876,000 which are assigned to the assignee of this invention and which are incorporated herein by reference. This system employes vertically spaced inflatable packer elements that are inflated through the action of a downhole pump that is operated in response to upward and downward movement of the pipe string. Although this system and the device described in the U.S. Pat. No. 3,439,740 have been widely used, both systems have a number of disadvantages. Where both packer elements are inflated by a single downhole pump, it is not possible for the operator at the surface to be absolutely sure that the lower one of the inflatable elements has obtained a reliable packer seat that will not leak during the performance of a drill stem test, because the actual condition of the lower packer, as to whether it is anchored and fully packed off, is masked to some extent by the upper packer. Also, in both the prior systems the respective packer elements are connected to the pump by common inflation passages that have in part taken the form of a "wash pipe" extending from the upper packer to the lower packer inside of a lengthly spacer pipe. Of necessity, the spacer and wash pipes are assembled in fairly short sections in a concentric configuration which has caused considerable difficulties in field assembly of the string of testing tools.
It is one object of the present invention to provide new and improved drill stem testing tools that utilize inflatable packer elements to isolate the well interval to be tested.
Another object of the present invention is to provide a new and improved inflatable packer testing system that includes functionally separate pumps for inflating the respective packer elements to enable a sequential expansion of the elements under full surface control of the operator.
Yet another object of the present invention is to provide a new and improved inflatable packer system that through use of separate pumps to inflate the lower and upper elements eliminates the previous requirement of an internal conduit connections between the upper and lower elements.
Still another object of the present invention is to provide a new and improved rotationally operable pump system that includes a unique mechanism for limiting the inflation pressure that can be supplied by the pump to an inflatable packer element in a well.